upload-pack: clear flags before each v2 request

Suppose a server has the following commit graph: A B \ / O We create a client by cloning A from the server with depth 1, and add many commits to it (so that future fetches span multiple requests due to lengthy negotiation). If it then fetches B using protocol v2, the fetch spanning multiple requests, the resulting packfile does not contain O even though the client did report that A is shallow. This is because upload_pack_v2() can be called multiple times while processing the same session. During the 2nd and all subsequent invocations, some object flags remain from the previous invocations. In particular, CLIENT_SHALLOW remains, preventing process_shallow() from adding client-reported shallows to the "shallows" array, and hence pack-objects not knowing about these client-reported shallows. Therefore, teach upload_pack_v2() to clear object flags at the start of each invocation. This has some other results: - THEY_HAVE gates addition of objects to have_obj in process_haves(). Previously in upload_pack_v2(), have_obj needed to be static because once an object is added to have_obj, it is never readded and thus we needed to retain the contents of have_obj between invocations. Now that flags are cleared, this is no longer necessary. This patch does not change the behavior of ok_to_give_up() (THEY_HAVE is still set on each "have") and got_oid() (used only in non-v2)); THEY_HAVE is not used in any other function. - WANTED gates addition of objects to want_obj in parse_want() and parse_want_ref(). It is also used in receive_needs(), but that is only used in non-v2. For the same reasons as THEY_HAVE, want_obj no longer needs to be static in upload_pack_v2(). - CLIENT_SHALLOW is changed as discussed above. Clearing of the other 5 flags does not affect functionality in v2. (Note that in non-v2, upload_pack() is only called once per process, so each invocation starts with blank flags anyway.) - OUR_REF is only used in non-v2. - COMMON_KNOWN is only used as a scratch flag in ok_to_give_up(). - SHALLOW is passed to invocations in deepen() and deepen_by_rev_list(), but upload-pack doesn't use it. - NOT_SHALLOW is used by send_shallow() and send_unshallow(), but invocations of those functions are always preceded by code that sets NOT_SHALLOW on the appropriate objects. - HIDDEN_REF is only used in non-v2. Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>